Selecting from a table where field = this and value = that - sql

Question

I have a mysql table that looks something like this:
Row 1:
'visitor_input_id' => int 1
'name' => string 'country'
'value' => string 'Canada'
Row 2:
'visitor_input_id' => int 1
'name' => string 'province'
'value' => string 'Alberta'
Row 3:
'visitor_input_id' => int 1
'name' => string 'first_name'
'value' => string 'Jim'
The problem is that I need to be able to filter it so that a user can generate reports using this:
filter 1:
'field_name' => string 'country'
'field_operator' => string '='
'field_value' => string 'Canada'
filter 2:
'field_name' => string 'province'
'field_operator' => string '!='
'field_value' => string 'Alberta'
filter 3:
'field_name' => string 'first_name'
'field_operator' => string '%LIKE%'
'field_value' => string 'Jim'
I am not really sure what the query would look like to be able to select from this using the filters. Any suggestions? (Unfortunately, creating a new table to store the data more sanely is not really feasible at this time because it is already full of user data)
I think it would look something like this:
if(field_name = 'province' THEN ADD WHERE field_value != 'Alberta')
if(field_name = 'country' THEN ADD WHERE field_value = 'Canada')
if(field_name = 'first_name' THEN ADD WHERE field_value LIKE '%jim%')
but I am not sure how that would work...

Answer 1

Turns out that this seems to work:
SELECT * FROM visitor_fields
INNER JOIN visitor_inputs ON (visitor_inputs.input_id = visitor_fields.input_id)
INNER JOIN visitor_fields as filter_0
ON (filter_0.input_id=visitor_inputs.input_id
AND filter_0.field_name = 'province'
AND filter_0.field_value != 'Alberta')
INNER JOIN visitor_fields as filter_1
ON (filter_1.input_id=visitor_inputs.input_id
AND filter_1.field_name = 'country'
AND filter_1.field_value = 'Canada')
INNER JOIN visitor_fields as filter_2
ON (filter_2.input_id=visitor_inputs.input_id
AND filter_2.field_name = 'first_name'
AND filter_2.field_value LIKE '%jim%')

Answer 2

I know you say creating a new table with a better schema isn't feasible, but restructuring the data would make it more efficient to query and easier to work with. Just create a new table (called visitor in my example). Then select from the old table to populate the new visitor table.
vistor
----------------
vistor_id
firstname
province
country
You could loop through the statement below with any scripting language (PHP, TSQL, whatever scripting language you're most comfortable with). Just get a list of all vistor_id's and loop through them with the sql below, replacing the x with the visitor_id.
INSERT INTO visitor (visitor_id, name, province, country) VALUES X,
(SELECT value FROM old_table WHERE name='first_name' AND vistor_id = x),
(SELECT value FROM old_table WHERE name='province' AND vistor_id = x),
(SELECT value FROM old_table WHERE name='country' AND vistor_id = x);
This will produce a table where all a visitor's data is on a single row.

Answer 3

Are you able to create an SQL string and then execute it? The string would look like this:
SELECT * FROM yourtable
WHERE (name='country' AND value='Canada') AND
(name='province' AND value!='Alberta') AND
(name='first_name' AND value LIKE '%jim%)
EDIT:
I see. Multiple records. So try joining them. This is not correct SQL syntax but should look similar:
SELECT * FROM
(SELECT * FROM yourtable WHERE (name='country' AND value='Canada'))
JOIN on visitor_input_id
(SELECT * FROM yourtable WHERE (name='province' AND value!='Alberta'))
JOIN on visitor_input_id
(SELECT * FROM yourtable WHERE (name='first_name' AND value LIKE '%jim%))